1. Field of the Invention
The present invention relates to a semiconductor laser device which is provided in an optical pickup apparatus used to record or reproduce information on or from an optical recording media.
2. Description of the Related Art
A semiconductor laser device is installed in an optical pickup apparatus and used to record or reproduce information on or from an optical recording media.
FIGS. 11A and 11B are simplified perspective views showing the construction of a semiconductor laser device 1 of the prior art. In the semiconductor laser device 1, a semiconductor laser chip 4 is mounted on one surface 3 of a first member 2 which is shaped into a circular disc and made of metal, and a heat sink 5 which efficiently diffuses heat generated when the semiconductor laser chip 4 emits a laser beam and a photodiode 6 which receives part of a light beam emitted from the semiconductor laser chip 4 and monitors laser output are firmly attached to each other by a die bond.
Optical output of the semiconductor laser chip 4 detected by the photodiode 6 is inputted to an APC (automatic power control), which is a system controller provided with a CPU (central processing unit) not shown in the drawings. The APC responds to optical detection output and controls a driving current of the semiconductor laser chip 4, thereby keeping output of the semiconductor laser chip 4 constant.
The semiconductor laser chip 4 and the photodiode 6 are electrically connected by wires 9 made of metal to lead pins 8. The lead pins 8 are fixed to the first member 2 and their surfaces are insulated by glass sealing parts 7. A hollow second member 15 made of metal is disposed so as to cover the semiconductor laser chip 4. The second member 15 is shaped like a cylinder having a bottom so as to have a peripheral wall 14 of a cylindrical shape and an end wall 13 which blocks a base end 12 of the peripheral wall 14. Accordingly, an opening 11 is formed on an open end 10 of the second member 15. To the end wall 13 of the second member, a laser beam emitting glass window 16 is disposed. At the open end 10 of the second member 15 is formed a flange 10a which protrudes radially outward from the circumference of the peripheral wall 14. The second member 15 is joined to the first member 2 by resistance welding in a state where an end face 17 of the flange 10a of the open end 10 abuts onto the one surface 3 of the first member 2.
At the time of attaching the semiconductor laser device 1 to an optical pickup apparatus, the one surface 3 of the first member 2 is made to adhere to an attachment face of the optical pickup apparatus, and fixed by a resin or the like after angular displacement of the semiconductor laser device 1 is made and a mounting position is adjusted so that a light beam emitted from the semiconductor laser chip 4 is focused in an appropriate position on an optical recording media. In an optical pickup apparatus provided with the semiconductor laser device 1, a light beam focused and reflected on an optical recording media is diffracted by a beam splitter or the like and focused on a signal reading photodiode, where signals are detected.
In cases where an optical pickup apparatus provided with a semiconductor laser device is installed in a portable optical disc player and the like, a semiconductor laser device is required to be small and lightweight for portable use. Another prior art for realizing miniaturization of a semiconductor laser device is disclosed in Japanese Unexamined Patent Publication JP-A 6-5990 (1994).
FIGS. 12A and 12B are simplified perspective views showing the construction of another semiconductor laser device 18 of the prior art. The semiconductor laser device 18 is characterized in that the projected shape onto the plane parallel to one surface 20 of a first member 19 is substantially elliptic. More specifically, in the first member 19, a part not used to mount the semiconductor laser chip 4 and so on is removed, whereby the device is miniaturized so as not to wastefully occupy a space when installed in an optical pickup apparatus or the like.
On one surface 20 of the first member 19 having a substantially elliptic shape, a heat sink 22 on which the semiconductor laser chip 4 and a signal reading photodiode 21 are mounted and the laser output monitoring photodiode 6 are firmly attached by a die bond.
A second member 23 is shaped like a cylinder having a bottom so as to have a peripheral wall of a substantially elliptic shape and an end wall 24 which blocks a base end of the peripheral wall. A laser beam emitting glass window 25 is disposed to an end wall 24 of the second member 23. A hologram device 26 is firmly attached on the laser beam emitting glass window 25 by an epoxy resin. The hologram device 26 is set and fixed so that, in order to obtain desired signals from reflection light from an optical recording media, diffracted reflection light is received in an appropriate position on the signal reading photodiode 21.
Also in this semiconductor laser device 18 of the other prior art, at an open end of the second member 23 is formed a flange 27a which protrudes radially outward from the circumference of the peripheral wall. The second member 23 is joined to the first member 19 by resistance welding in the state where an end face 28 of the flange 27a of the open end 27 abuts onto the one surface 20 of the first member 19.
Moreover, at the time of measuring characteristics such as threshold current values, oscillation modes and the like of the semiconductor laser devices 1, 18, the semiconductor laser devices 1, 18 are mounted on a mounting portion of a measurement apparatus at the one surfaces 3, 20 of the first members 2, 19, whereby each measurement is done.
The semiconductor device 1 of the aforementioned prior art and the semiconductor laser device 18 of the other prior art have the following problems.
As described before, the first members 2, 19 provided in the respective semiconductor laser devices 1, 18 are joined to the second members 15, 23 by resistance welding at the one surfaces 3, 20. In resistance welding, spatters, which are droplets of molten metal, are generated frequently, and when spatters are generated, the spatters fuse with the one surface, or even when not fuse, because of collisions of the spatters, rough and large irregularities are formed at collision spots on the one surface. There is such a problem that after the second member and the first member are joined together, when the first member is attached to an attachment portion of, for example, an optical pickup apparatus or a measurement apparatus at the one surface of the first member, the spatters fusing on the one surface of the first member and the rough and large irregularities formed thereon worsen attachment precision to the apparatus.
Moreover, although it can be thought to mount to an apparatus by making the first member larger and using a rim portion of the first member, which is rarely influenced by spatters due to resistance welding, as one means for solving the problem on the one surface caused by resistance welding, there is such a problem that in cases where the device is used in an optical pickup apparatus installed in a portable optical disc player and the like as described before, the device becomes larger by making the first member larger, and handiness and portability of a portable optical disc player are impaired.
An object of the present invention is to provide semiconductor laser device which can be attached to a desired apparatus with precision by preventing roughness of a surface of a joint member due to welding.
The invention provides a semiconductor laser device, comprising:
a semiconductor laser chip for emitting a laser beam;
a first member on which the semiconductor laser chip is mounted, the first member having one surface substantially perpendicular to an emission direction of a laser beam from the semiconductor laser chip in the state of being mounted, and a concave having a bottom face substantially parallel to the one surface, and the semiconductor laser chip being disposed to the bottom face of the concave; and
a second member shaped like a cylinder having a bottom, an open end of the second member being inserted into the concave to mount the second member on the first member so as to cover the semiconductor laser chip.
According to the invention, the first member has one surface substantially perpendicular to an emission direction of a laser beam from the semiconductor laser chip, and has a concave having a bottom face substantially parallel to the one surface, and the semiconductor laser chip is disposed to the bottom face of the concave. Into the concave of the first member, the open end of the second member which is shaped like a cylinder having a bottom is inserted, and the second member is joined to, that is, mounted on the first member at the concave so as to cover the semiconductor laser chip. Consequently, it is avoided that when the first member and the second member are joined together by, for example, resistance welding, fusion of spatters generated at the time of resistance welding and wastage due to collisions of the spatters (such a state that smoothness of the one surface is impaired will be referred to as roughness hereafter) are caused on the one surface of the first member, with the result that it is possible to attach the first and second members after being joined together to a desired apparatus with precision.
Further, in the invention it is preferable that on the open end of the second member a protrusion which protrudes toward an insertion direction is formed; and
the second member is joined to the bottom face of the concave via the protrusion.
According to the invention, the second member is joined to the first member at the bottom face of the concave via the protrusion, which is formed on the open end and protrudes toward an insertion direction into the concave of the first member, so that it is avoided to cause roughness on the one surface of the first member, and the second member is securely fused and joined to the first member by the protrusion. As a result, it is possible to attach the first and second members after being joined together to a desired apparatus at the one surface with precision.
Still further, in the invention it is preferable that around the open end of the second member, a protrusion which protrudes outward from the second member, and the second member is joined to a wall face of the concave via the protrusion.
According to the invention, the second member is joined to the first member at the wall face of the concave via the protrusion formed around the open end and protruding outward, so that it is avoided to cause roughness on the one surface of the first member, and the second member is securely fused and joined to the first member by the protruding. As a result, it is possible to attach the first and second members after being joined together to a desired apparatus at the one surface with precision.
Still further, in the invention it is preferable that on the second member, a notch portion which extends in a direction parallel to a direction of inserting the second member into the concave is formed.
According to the invention, on the second member, the notch portion extending in a direction parallel to a direction of inserting the second member into the concave is formed, so that it becomes possible to insert such a second member that has a larger size than an opening size of the concave, and it is possible to join the wall face of the concave and the second member to each other with no space.
Still further, the invention provides an optical pickup apparatus comprising:
a semiconductor laser device including:
a semiconductor laser chip for emitting a laser beam; a first member on which the semiconductor laser chip is mounted; a first member having one surface substantially perpendicular to an emission direction of a laser beam from the semiconductor laser chip in the state of being mounted, and a concave having a bottom face substantially parallel to the one surface, on a bottom face of which concave the semiconductor laser chip is disposed; and
a second member which is shaped like a cylinder having a bottom, an open end of the second member being inserted into the concave to mount the second member on the first member so as to cover the semiconductor laser chip;
focusing means for focusing the light beam emitted from the semiconductor laser device to an optical reflector and for conducting light reflected from the optical reflector to the semiconductor laser device; and
optical detecting means for detecting the light reflected by the optical reflector and conducted by the focusing means.
According to the invention, it is possible to precisely attach the semiconductor laser device to the optical pickup apparatus at the one surface of the first member without applying a care process for smoothing the one surface of the first member after joining the first member and the second member to each other. As a result, it is possible to realize reduction of manufacturing man-hour of the optical pickup apparatus, and it becomes possible to accurately focus an emission light beam from the semiconductor laser device by the focusing means in a focusing position of an optical recording media, which is an optical reflector, and precisely detect signals of reflection light from the optical recording media by the optical detecting means.
According to the invention, the open end of the second member is inserted into the concave formed on the one surface of the first member, and the second member is joined to the first member at the concave so as to cover the semiconductor laser chip and so on, with the result that it is avoided to cause roughness on the one surface of the first member. Consequently, it is possible to attach the first and second members after being joined together to a desired apparatus at the one surface with precision.
Further, according to the invention, it is possible to precisely place the semiconductor laser device to the optical pickup apparatus at the one surface of the first member without applying a process for smoothing the one surface of the first member. As a result, it is possible to realize reduction of manufacturing man-hour of the optical pickup apparatus, and it becomes possible to accurately focus an emission light beam from the semiconductor laser device by the focusing means in a focusing position of an optical recording media, and precisely detect signals of reflection light from the optical recording media by the optical detecting means.